title: Differences in doxorubicin-induced apoptotic signaling in adult and immature cardiomyocytes.
abstract: A proposed mechanism for the cardiotoxicity of doxorubicin (DOX) involves apoptosis in cardiomyocytes. In the study described here, we investigated the molecular basis for the differences in DOX-induced toxicity in adult rat cardiomyocytes (ARCM), neonatal rat cardiomyocytes (NRCM), and rat embryonic H9c2 cardiomyoblasts. Activation of caspase-9 and -3 was considerably lower in DOX-treated ARCM as compared with NRCM and H9c2 cardiomyoblasts. Addition of cytochrome c caused the activation of caspase-9 and -3 in permeabilized NRCM and H9c2 cardiomyoblasts but not in permeabilized ARCM. Expression of proapoptotic proteins, apoptotic protease activating factor-1 (Apaf1), and procaspase-9 was significantly lower, and abundance of antiapoptotic X-linked inhibitor of apoptosis protein (XIAP) was higher in ARCM, as compared with immature cardiac cells. Despite the abundance of XIAP in ARCM, its role in the inhibition of apoptosome function was dismissed, as second mitochondria-derived activator of caspases (Smac)-N7 peptide, had no effect on caspase activation in response to cytochrome c in these cells. Adenoviral expression of Apaf1 exacerbated the activation of caspase-9 and -3 in DOX-treated NRCM, but did not increase their activities in DOX-treated ARCM. This finding points to a major difference in the apoptotic signaling between immature and adult cardiomyocytes. The mitochondrial apoptotic pathway is limited in ARCM treated with DOX.
authors.affiliation: Department of Biophysics and Free Radical Research Center, Medical College of Wisconsin, Milwaukee, WI 53226, USA. ekonorev@hawaii.edu
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Konorev
authors.forename: Sravan
authors.initials: S
authors.lastname: Vanamala
authors.forename: Balaraman
authors.initials: B
authors.lastname: Kalyanaraman
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D053478:Apoptosomes / Q000187:drug effects* / Q000378:metabolism; D053477:Apoptotic Protease-Activating Factor 1 / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D015151:Immunoblotting; D008297:Male; D024101:Mitochondrial Proteins / Q000378:metabolism; D032386:Myoblasts, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D013347:Subcellular Fractions; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; C506594:Apaf1 protein, rat; D051017:Apoptosis Regulatory Proteins; D053478:Apoptosomes; D053477:Apoptotic Protease-Activating Factor 1; D002352:Carrier Proteins; C489013:DIABLO protein, rat; D024101:Mitochondrial Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; D004317:Doxorubicin; D045304:Cytochromes c; D020169:Caspases